Crystallux can be found in Belinsk Opera House when the Grave Eclipse has started. You go to the back the building, where the stage is, and you see the girl trying to protect it, but monsters bash her aside. Then it is up to you to fight the monsters and win Crystallux, which the girl tells you to protect.
According to stories passed about by residents, Crystallux hid as a chandelier in Belinsk Opera House due to a love of music. A girl in the opera house believed the stories, and would leave food out at night for Crystallux. Though she never saw the dragon, the food was gone the next day.
When the Grave Eclipse hit, Belinsk's soldiers managed to barricade several monsters in the Opera House. Led by King Volechek, the soldiers entered the Opera House when they realized the monsters were making no noise. The scene appeared as a vision to Sveta, Volechek's sister, and a member of Matthew's group, The vision led Matthew to rush to the Opera House to investigate.
At the Opera House, Matthew found the soldiers dead, with three monsters appearing on stage. Suddenly, Crystallux manifested as its dragon form, and appeared to confront them. The girl, who was watching nearby, attempted to protect Crystallux, but was knocked aside. Matthew successfully defeats the monsters, but the girl died of her injuries, though not before briefly speaking to the dragon. Crystallux manages to communicate its desire to assist Matthew, and so his party of Adepts is granted the ability to summon Crystallux in battle.
Crystallux can be considered an upgraded version of the Judgment summon, being 25% stronger than Judgement. In some ways, it can be considered as a counterpart to the Jupiter-based Eclipse summon, which is identical in damage potential, and is similarly an upgrade to the Thor summon. Until the player can acquire Charon, Crystallux is also the strongest Venus-based summon available. Since Charon can only be accessed after the defeat of the final boss, it becomes the premier Venus summon for the latter part of the game. Crystallux is unique among the Summons in that it can reduce the Resistance of the targets. Thus, it is useful at the beginning of the battle to weaken an enemy, as most forms of damage available to the player are influenced by Elemental Power and Resistance to a degree. However, if trying to take advantage of elemental weaknesses, there are fewer options, as there are few bosses with a specific weakness against Venus. Despite this, Crystallux's chance of reducing Resistance means that it remains an excellent option for most battles.
Crystallux originally appeared in the commercial for the first Golden Sun, about 10 years before its official debut in Golden Sun: Dark Dawn.
- As a reference to the commercial, the Summon is obtained in Belinsk Opera House, and its summoning sequence takes place inside of an opera house not unlike the one where the commercial takes place.
- In addition, Crystallux was destroyed at the end of the commercial, shattering into pieces. The summoning sequence in Dark Dawn begins with Crystallux reconstructing itself from the shattered glass/crystals of the chandelier.